1. Field of the Invention
This invention relates to a temperature adjustment method for metal molds in an injection molding system that prepares a plurality of movable metal molds, divides a series of a molding process such as mold clamping, injection, pressure retention, cooling, mold opening, mold release of a molding (and insert setting in the case of insert molding) and conducts in parallel the molding operations at a plurality of stations and serially conveys the metal molds. The invention also relates to an injection molding machine for this method.
2. Description of the Related Art
An injection molding system of the type which moves a plurality of metal molds in one direction such as a linear conveying system injection molding machine shown in FIG. 4 and a rotary table system injection molding machine shown in FIG. 5 have been proposed in the past by Japanese Unexamined Patent Publication No. 58-173635 and so on, for example.
Generally, in the injection molding system as mentioned above, in order to maintain a stable temperature of the mold, a method of cooling or heating a mold connected to pipes through which a cooling medium or a heating medium flows, and of heating a mold by means of a cartridge heater inserted into the mold and connected to electric wires are known, as proposed by Japanese Unexamined Patent Publication No. 3-207619, for example. That is, in Publication No. 3-207619, the cartridge heater or a thermocouple imbedded into the mold is connected to a control device, which is an electric source, via a rotary joint, and the temperature of the mold is controlled to the temperature required for resin molding.
However, because the metal molds are moved in rotation in one direction according to such prior art systems, connection by a rotary joint is indispensable to always keep a piping arrangement, for a cooling medium or a heating medium, connected, to the metal molds. The rotary joint has the problem of durability of a seal because it has a slide surface, and is therefore not free from the frequent occurrence of leakage of water.
When a cartridge heater or a thermo-couple is employed, electric power must be supplied through electric wires by using slide contacts such as slip rings. This method is not free from the problem of wear of brushes, either, and is not suitable at a mold temperature requiring cooling because temperature adjustment by heating solely depends on the heater.
Furthermore, these piping arrangements and electric wires get more complicated with the increase of the number of metal molds, and the number of metal molds that is used in practice is not greater than four.